The electronics industry is continually called upon to make products smaller and more powerful. Applications such as mobile phones, portable computers, computer accessories, hand-held electronics, etc., create a large demand for smaller electrical components. These applications further drive technology and promote the research of new areas and ideas with respect to miniaturizing electronics. The technology is often limited due to the inability to make certain components smaller, faster, and more powerful. In addition, manufacturing concerns can make the cost of production exceedingly expensive. For example, the use of complicated processes, a large number of steps, and/or a number of different machines or parts quickly drives up the cost of manufacturing electronic components.
Magnetic components, such as inductors, are good examples of the type of components that have been forced to become smaller and/or more powerful. Typical inductors include shielded and non-shielded components. Non-shielded components are often used in low current applications and comprise a wire wound about a core of magnetic material, such as ferrite, with the ends of the wire connected to respective terminals for mounting the component into an electronic circuit of some type, usually on a printed circuit board. Due in part to the difficulty in metalizing the core itself, the core of these components is usually nested in a body of ceramic or plastic material to which the terminals are connected.
Shielded components are often preferred due to the efficiency with which they allow the inductive component to operate and due to the minimal interference they have on the remainder of the circuit, regardless of whether it is a low or high current application. Shielded components often comprise a wire wound into a coil with the ends of the wire connected to respective terminals for mounting the component into a circuit, much like non-shielded components. Shielded components, however, typically include a shielding body encasing all or a large portion of the coil winding so that the inductor is able to operate more efficiently and generates only minimal electromagnetic interference.
For example, some inductive components use a cover made of either a magnetic or non-magnetic material in order to reduce the amount of gaps and close the flux paths associated therewith so that the component operates more efficiently and better inductance characteristics can be reached. Examples of such structures can be seen in U.S. Pat. No. 3,750,069 issued to Renskers on Jul. 31, 1973, U.S. Pat. No. 4,498,067 issued to Kumokawa et al. on Feb. 5, 1985, U.S. Pat. No. 4,769,900 issued to Morinaga et al. on Sep. 13, 1988, and U.S. Pat. No. 6,717,500 issued to Girbachi et al on Apr. 6, 2004. Although these patents illustrate such covers for use with specific windings and core shapes, it should be understood that such concepts may apply to other windings and core shapes, as desired.
A shortcoming of such structures, however, is that the shielding accomplished by the cover often takes up additional space and allows for unnecessary air gaps to exist in the component. This shortcoming has been addressed by embedding the coil in magnetic and/or non-magnetic materials for shielding purposes. The embedded coil may either be potted and cured such as in U.S. Pat. No. 3,255,512 issued to Lochner et al. on Jun. 14, 1966, or compression molded and cured such as in U.S. Pat. No. 3,235,675 issued to Blume on Feb. 15, 1966, U.S. Pat. No. 4,696,100 issued to Yamamoto et al. on Sep. 29, 1987, U.S. Pat. No. 6,204,744 issued to Shafer et al. on Mar. 20, 2001 and U.S. Pat. No. 6,759,935 issued to Moro et al. on Jul. 6, 2004.
Typically, the cured components include a wire embedded in a magnetic and/or non-magnetic mixture which contains a binder such as epoxy resin, nylon, polystyrene, wax, shellac, varnish, polyethylene, lacquer, silicon or glass ceramic, or the like, in order to hold the mixture together. Magnetic materials, such as ferrite or powder iron mixtures, and/or non-magnetic material, such as other metals and powdered metal mixtures, may be used in combination with the binder to form the mixture used to embed the coil winding. The mixture is then potted and cured to form a hardened inductor capable of being inserted into a circuit via conventional pick-and-place machinery.
One type of compression molded component includes a wire embedded in a similar magnetic and/or non-magnetic mixture, however, the mixture typically contains a plastic or polymer binder which is capable of withstanding the high temperatures at which the molded structure (or the green body) will be baked or sintered. Compression molding is often preferred over curing in that it allows for a more densely populated mixture with minimal gaps between molecules, which in turn can improve the inductance characteristics of the component and reduce flux losses. However, since compression molding is often several times more expensive than potting and curing with a binder such as epoxy, potted and cured components are typically pursued in applications for which they are capable of meeting the desired operational parameters.
Another factor that weighs in heavily as to whether curing or compression molding is used and as to what type of mixture is used, (e.g., magnetic and/or non-magnetic), is whether the component is meant for high current, low inductance applications or for low current, high inductance applications. In high current, low inductance applications, compression molding is often used due to its ability to densely pack the shielding material around the coil winding. In such applications, the mixture is typically made of a non-ferrite powdered iron magnetic and/or non-magnetic material in combination with a polymer binder, such as resin. The powdered iron material used in such applications has a larger saturation magnetic flux density and a relatively low permeability as compared to ferrite. A flat winding of wire is also typically used in place of a round wire due to its ability to handle higher current without adding the size associated with a larger gauge, round wire. One shortcoming with existing high current, low inductance applications, however, is that the number of windings cannot be increased without the footprint of the component also increasing. This is due to the fact conventional components only wind the flat conductors used for the wire coil in a single row of wire. Thus, as the number of windings are increased, so too must the footprint of the component be increased.
Another shortcoming with conventional high current, low inductance applications is that components with the same general structure cannot be used to form low current, high inductance applications due to the negative attributes associated with non-ferrite magnetic and/or non-magnetic mixtures. For example, components made of lossy materials such as powdered iron without ferrite often have poor direct current resistance (“DCR”) and lower Q values when used in low current, high inductance applications which can hinder the performance and efficiency of the component. Thus, the lack of a ferromagnetic material such as ferrite can leave the component incapable of reaching the inductance levels that may be required for certain low current, high inductance applications.
Yet another shortcoming with conventional components is that they either require the wire to be pre-wound and then removed from the object it is wound upon (which is often difficult to accomplish) and inserted into a mold to be encased in the magnetic and/or non-magnetic mixture via potting or compression molding, or they require multiple steps to produce the end component, such as by requiring the use of multiple dies to form the component.
Accordingly, it has been determined that the need exists for an improved inductive component and method for manufacturing the same which overcomes the aforementioned limitations and which further provide capabilities, features and functions, not available in current devices and methods for manufacturing.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and/or relative positioning of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention. It will also be understood that the terms and expressions used herein have the ordinary meaning as is accorded to such terms and expressions with respect to their corresponding respective areas of inquiry and study except where specific meanings have otherwise been set forth herein.